KR960011889B1 - Method for treatment of waste water from reclaimed land - Google Patents

Abstract

The waste water of 100-300ppm COD obtained from reclaimed land is treated with 100ppm iron compound selected from FeCl3, FeCl2 and FeSO4 for 20-60 min. in reactor adjusting pH 5.6-8.6 by sulfuric acid or sodium hydroxide, and cohering previous reactants with polyacrylamide as coagulant, and separating solid and liquid in settling bath, and filtering upper liquid with sand filter(S/F).

Description

Leachate Treatment of Inorganic Sludge Landfill

1 is a schematic diagram of a leachate treatment method by a warming treatment of the prior art.

2 is a schematic view of a leachate treatment method according to the present invention.

3 is a graph showing the change of COD according to the amount of FeCl _{3 in the} leachate.

4 is a graph showing the change of COD according to the reaction time when a certain amount of FeCl _{3 is} added.

5 is a graph showing the change of SS (floating matter) according to the FeCl ₃ input amount in leachate.

The present invention relates to a method for treating leachate in an inorganic sludge landfill, in particular, a method for treating low concentration pollutant-containing leachate in a small scale inorganic sludge landfill.

In general, the problems associated with environmental pollution in leachate from sludge landfills are COD (Chemical Oxygen Demand) and SS (Suspendid Solid). By the way, the leachate of an inorganic sludge landfill site is especially low in COD components in many cases. In the present invention, regardless of the high and low SS component concentration, the leachate treatment method when the leachate COD is low (100-300ppm), in particular, the acupuncture treatment method of a small inorganic sludge landfill with a daily wastewater discharge of about 3000m ³ or less It is about.

Inorganic sludge is usually generated in large quantities in water treatment processes. Water treatment plants in which ordinary inorganic sludge is generated have a main purpose of removing suspended solids (SS) in the wastewater, but also include a small amount of oil and organic components. In developed countries such as Japan, inorganic sludge is already disposed of in landfills in management type, and in Korea, inorganic sludge generated in water treatment process has been legislated as landfill in management type since 1994. On the other hand, in the case of landfill disposal of inorganic sludge, since acupuncture water is generated in an inorganic sludge landfill, it is required to treat the leachate in order to catch environmental pollution.

Regarding legal regulations, conventional leachate treatment methods are primarily directed to treating leachate from organic sludge landfills. Leachate from organic sludge landfills has a chemical calorific demand (COD) of about 10,000 ppm, which is mainly used for biological treatment. However, since the leachate of the inorganic sludge landfill has a chemical oxygen demand of usually 100 pm or less, there is a problem in applying the organic sludge leachate treatment method as it is. That is, the biological treatment method, which is usually used for the leachate treatment of organic sludge landfill, has a large scale because of the aerobic treatment after the anaerobic treatment. Therefore, the inorganic sludge landfill leachate treatment uses the ozone oxidation method such as the first degree. In general, the conventional method is described in detail with reference to FIG. 1 as follows. As shown in FIG. 1, in a conventional method, ozone is blown into a first adjusting tank to oxidize a causative agent of COD, and a hydrogen ion is used in an chemical tank using an acid (H ₂ SO ₄ ) or an alkali (NaOH). Adjust the concentration (pH). Particles produced during this reaction and suspended solids (SS) contained in the leachate are aggregated into a flocculant (polyaluminum chloride (PAC) and a polymer flocculant), and they are precipitated in a sedimentation tank. On the other hand, suspended particulates not removed in the sedimentation tank are removed through a sand filter (S / F: Sand Filter), and the COD-causing substances not removed by ozone in the leachate passed through the sand filter are activated carbon filters (C / F: Carbon). Filter), and the leachate passed through the activated carbon filter (C / F) is discharged through the second adjustment tank. The main problem with the above-described conventional method is that ozone is used to remove the COD causative agent. In other words, the ozone generator is not only expensive, but also requires a lot of operation (power ratio). It is also known that changes in the concentration of pollutants in leachate generally change over time. In other words, the concentration of contaminants in leachate gradually increases with time after landfill, but after the landfill reaches a certain point (known as 3-6 years for urban waste) Decreases gradually. Therefore, the performance of the ozone generator should be installed on the basis of the maximum pollutant concentration. Therefore, in the leachate treatment facility which is usually used for about 20 years, most of the facilities are overinvested by installing the ozone generator over the appropriate scale. Along with this, the biggest shortcoming of ozone treatment is the inability to remove hard-line polymers from leachate. In most cases, the ozone reacts with the hardly decomposable polymers in the leachate, which results in a side effect of the COD of the treated water being higher than that of the raw water. That is, since the COD-causing substance generated in the inorganic sludge is a hardly decomposable compound, it is difficult to completely decompose by ozone.

The present invention is intended to provide a new method that can effectively treat the leachate of the inorganic sludge landfill without using ozone by supplementing the fastening point of the prior art method described above.

According to the present invention, a method of treating leachate from an inorganic sludge landfill having a COD concentration of about 100-300 ppm through a reactor (chemical tank) introduced into a control tank includes: FeCl ₃ , FeCl _2, FeSO _4, and mixtures thereof The iron compound selected from the leachate was added to the reaction tank by 100 ppm or more based on the leachate, and the pH of the reaction solution was adjusted to 5.6-8.6 using a pH adjuster (acid or base) for about 20-60 minutes, followed by adding a polymer flocculant. The flocculation of the inorganic sludge landfill disposer is provided, characterized in that the flocculant, the resulting mixture is introduced into the settling tank to separate the solids, and then the supernatant is filtered through a sand filter (S / F). When described with reference to the accompanying drawings as follows.

As shown in FIG. 2, the process of the present invention is carried out in a reaction system comprising a first bath, a reactor, a precipitation tank, a sand filter (S / F) and a second bath, wherein each means of the reaction system is known in the art. Functions similar to

The first adjusting tank is a means for maximizing the efficiency of the first reactor by storing the leachate generated and supplying the leachate to the reactor constantly.

The reactor is a means for removing hardly decomposable compounds, which are the most COD-causing substances generated in the inorganic sludge, and the ferrous compound selected from FeCl ₃ , FeCl ₂ , FeSO ₄ and mixtures thereof (acid A), acid (drug C) ) And a base adjuster selected from a base (Drug D), and a polymer coagulant (Drug B).

The first action of the iron compound (Drug A) in the reactor is to form a complex with the COD-causing agent from the inorganic sludge. In order to generate inorganic sludge in the water treatment process, a coagulation precipitation process is performed. Here, a polymer flocculant is added for flocculation, and most organic matter in the inorganic sludge is this. As such a polymer flocculant, any conventional polymer flocculant may be used, and the most used one is polyacrylamide (PAA) having the following structural formula.

On the other hand, when the inorganic sludge containing a large amount of polyacrylamide is embedded, part of the polyacrylamide is decomposed or polymerized by the embedded earth pressure, heat, and microorganisms. The leachate thus contains polyacrylamide itself or a decomposed polyacrylamide compound having a functional group of polyacrylylamide. In other words, among the COD-causing substances generated in the inorganic sludge, many organic substances have functional groups such as C = 0, C = NH, CH-NH _{2, and the} like, because of the flocculant contained in the inorganic sludge.

In the present invention, by using an iron compound selected from the group consisting of inexpensive and easily available FeCl ₃ , FeCl ₂ , FeSO ₄ and mixtures thereof, a polymer coagulant compound such as polyacrylamide in leachate is converted into a complex such as I found it possible.

The second action of the iron compound (Drug A) is to agglomerate the COD-causing substances from suspended solids and substances in leachate, or from inorganic sludge that becomes complex and insoluble by:

Fe ³⁺ and Fe (OH) ₃ produced in the above reaction are suspended solids in leachate and complexes with substances or COD-causing substances, which becomes insoluble and then floats in inorganic sludge as the pH is adjusted. Coagulation of solids, substances and COD causative agents.

Drug B, which can be selected and used from conventional polymer coagulants well known in the art, functions to crosslink flocculation of a material aggregated by an iron compound (Pharmaceutical A), and preferably a polyacryl as mentioned above. Amide.

The acid (drug C) base (drug D), which is a pH regulator, promotes aggregation and condensation and regulates the pH of the discharged wastewater within the statutory criteria. The acid or base is selected depending on the nature of the leachate. As the acid (Drug C), various conventional acids can be used, but sulfuric acid (H ₂ SO ₄ ) is particularly preferable in terms of promoting aggregation and condensation in the reactor. As the base (drug D), various conventional bases can be used, but sodium hydroxide (NaOH) is particularly preferred.

The settling tank serves to settle and remove suspended solids condensed in the reaction tank, and the sand filter (S / F) removes fine suspended solids from the leachate treated in the settling tank, and the second adjusting tank removes the treated leachate. Collect and release.

As can be seen from the examples to be described later and in FIGS. 3-5, the iron compound has a satisfactory result when it is added at a concentration of 100 ppm or more based on the leachate, and the reaction time in the reactor is not particularly limited, but 20-60. Minute ranges have been found to be preferred.

The present invention will be described through the following examples.

Example 1

After dissolution of two kinds of inorganic sludge produced in steel mill process, the leaching water is produced by legal dissolution method (leach water is generated over a long time after landfilling, and usually the leaching test predicts the water quality by leaching test according to the legal method). FeCl ₃ was added to the result, and the result similar to the 3rd degree was obtained. In other words, when 200 ppm or more of FeCl ₃ is added to the effluents having a COD concentration of 240 ppm and 210 ppm, the effluent COD is reduced to less than 150 ppm COD, which is a legal standard of a company having a daily wastewater discharge rate less than 3000 m ³ .

Example 2

When FeCl ₃ was introduced at a concentration of 500 ppm in the leachate having an initial COD concentration of about 180 ppm, the COD change was observed at the reaction time, and the results are shown in FIG. 4.

In the graph of the figure, the optimum reaction time was found to be 20-60 minutes.

Example 3

The inorganic sludge from the mill water treatment step elution method the FeCl ₃ to elution can then molten iron in accordance with (to be occur over the leachate is a long time after filled, Average predict the quality of the leachate to the leaching test according to the statutory methods) As a result, the same result as in FIG. 5 was obtained. That is, SS is the concentration is seen that when the power is applied the FeCl ₃ to be eluted in the vicinity of 265ppm, when turned to 100ppm or more FeCl ₃ 1 days wastewater emissions to SS 150ppm less than the statutory standards of 3000m of less than ³ areas.

Through the above examples, it was proved that the present invention has the following advantages when treating leachate.

First, this treatment method has the advantage of lower equipment costs than the ozone treatment method. That is, it is not necessary to install an ozone generator and an activated carbon adsorption tower.

Second, since the present invention is a chemical treatment, it is possible to effectively cope with changes in the contaminant concentration of the leachate compared to the conventional method. That is, the contaminant concentration of the leachate changes over time. According to the present invention, only the chemical dosage can be adjusted. However, the conventional method has to be designed according to the highest concentration of the leachate, so there is no choice but to invest in excess capacity.

Third, when the present invention is applied to the landfill site less than 3000m ³ of the amount of leachate per day, it is expected that the investment and operating costs can be minimized, especially in small landfills.

Claims (2)

In a method of treating leachate from an inorganic sludge landfill site having a daily leachate less than 300 m ³ and a COD concentration of 100-300 ppm, after the inflow into the control tank through a reaction tank (Chemical tank), FeCl ₃ , FeCl ₂ , FeSO ₄ and 100 ppm or more of the iron compound selected from the group consisting of the mixture was introduced into the reactor and the pH of the reaction solution was adjusted to 5.6-8.6 using a pH adjuster (acid or base), followed by reaction for 20 to 60 minutes. Injecting the coagulant, the resulting mixture is introduced into the settling tank to separate the solids, and then the supernatant is filtered through a sand filter (S / F), leachate treatment method of inorganic sludge landfill disposal site. The method of claim 1, wherein the iron compound is FeCl ₃ , the polymer coagulant is polyacrylamide, the acid is sulfuric acid in the pH adjuster, the base is sodium hydroxide, leachate treatment method of the inorganic sludge landfill.